There has been disclosed a wafer for a semiconductor device where an impurity-containing oxide film, e.g., a tetra ethyl ortho silicate (TEOS) film, produced by a chemical vapor deposition (CVD) or the like; an electrically conductive film, e.g., a titanium nitride (TiN) film; a bottom anti-reflective coating (BARC) film; and a mask layer (photoresist film) are stacked in that order on a silicon substrate (see, e.g., Japanese Patent Application Publication No. 2006-190939 and corresponding US patent Application Publication No. 2006-0141766 A1). The photoresist film is processed to have a predetermined pattern by photolithography and serves as a mask layer when the BARC film and the conductive film are etched.
As the scaling down of semiconductor devices has recently been in progress, it is needed to form a finer circuit pattern on a surface of the wafer described above. In order to form such a finer circuit pattern, it is required to form a small-sized opening (a via hole or a trench) on an etching target film by reducing a minimum feature dimension of the pattern of the photoresist film in the manufacturing process of a semiconductor device.
In order to form the small-sized pattern on the photoresist film, a highly transparent material may be employed to improve a pattern transfer fidelity by an exposure light. Since, however, such a highly transparent material has a low hardness, the strength of the mask layer is deteriorated. As a result, it becomes difficult to obtain a satisfactory etching resistance.
As such, a formation of a finer pattern and an etching resistance of a material are in a trade-off (antinomy) relationship in the mask layer.
There has been disclosed a technique for improving the etching resistance of a mask layer in the manufacturing process of a semiconductor device (see, e.g., Japanese Patent Application Publication No. 2007-005598 and corresponding US patent Application Publication No. 2009-0029284 A1)
In this Japanese Patent Application Publication, a technique for forming a mask has been disclosed. Specifically, a mask layer is coated with a pattern coating material containing a metal compound capable of producing a hydroxyl group by hydrolysis, the pattern coating material being employed in an etching process of etching a base layer by using patterns formed on a substrate as the mask layer. Then, by bringing water or deionized water into contact with the pattern coating material, the metal compound is hydrolyzed thereby producing the hydroxyl group. As a result, an etching-resistant mask including the metal oxide is formed.
Since, however, the strength of the mask layer formed by such a conventional method is not satisfactory, it is needed to develop a satisfactory etching-resistant mask layer formed with a fine pattern.